Multiple indirection in c language

Answer 1

C uses pointers for indirection. So, using a pointer to a pointer would be multiple indirection. For example, the following code uses multiple indirection:

int i = 42;

int *pi = &i;

int **ppi = π

**ppi++;

printf("i is now %d\n", i);

Answer 2

The unary indirection operator (*) is used to dereference a pointer to a type or a function in order to convert it to an l-value or a function designator, respectively.

For instance, if you declare a pointer to an int type as follows:

int * i = new int(10);

Then i contains the memory address (typically 32-bit or 64-bit depending on the architecture) where the integer value 10 was allocated on the heap (the free store). To dereference this pointer to determine the value stored at that memory address, or indeed to alter the value at that memory location, we use the unary indirection operator, as follows:

if( *i == 10 )

*i = 5;

Note that the value of i has not changed -- it still contains the same memory address. But the value stored at that memory address will have been changed from 10 to 5. This can be proved by outputting both the value of i and the dereferenced value of i, both before and after changing the dereferenced value, such as:

int * i = new int(10);

printf( "Before:\n" );

printf( "Direct value of i: 0x%.8x, indirect value of i: %d\n\n", i, *i );

*i = 5;

printf( "After:\n" );

printf( "Direct value of i: 0x%.8x, indirect value of i: %d\n\n", i, *i );

Example output:

Before:

Direct value of i: 0x010255f3, indirect value of i: 10

After:

Direct value of i: 0x010255f3, indirect value of i: 5

Answer 3

Access data via pointer. Eg:

*p, p->field

Answer 4

It's the arrow "->"

And the asterix "*"